Tectonic and sedimentary evolution of the Ofanto thrust-top basin

The Ofanto basin is a wide synclinorium, about 30 km in length, located between the axial and external zones of the Southern Apennine chain and characterised by an unusual E-W trend (Fig. 1). The substratum of this Pliocene basin is formed by pelagic units of the Southern Apennines Allochtonous (SAA) (i.e. Sicilide and Lagonegro Units), with overlying Late Miocene siliciclastic deposits of the Castelvetere Flysch. Well data constrain the age of thrusting of the SAA on the Apulian Carbonate Platform as Early Pliocene in this sector of the chain. Coeval to the migration of the SAA was the deposition of Pliocene marine sediments of the Ariano Unit on top of the translating thrust sheets. The E-W trend of the Ofanto synclinorium represents an anomaly in the regional NW-SE structural trend of the Southern Apennines, which has been attributed either to major (lithospheric) strike-slip faults (Ortolani 1974; Schiattarella et al. 2005), or to the effect of deep thrust faulting in the Apulian Platform (Hyppolite et al. 1994). This work integrates the analysis of the synorogenic Ofanto basin together with the interpretation of about 300 km of reflection seismic lines and well data to define: a) the syntectonic characteristics of the Ofanto basin infill and its age based on new biostratigraphic studies; b) the 3-D geometry of the Ofanto basin evolving during the coeval emplacement of the SAA and subsequently deformed by the shortening that affected the underlying Apulian carbonate platform; c) the tectonic evolution and timing of deformation of this segment of the Apennine fold and thrust belt.